1. Field of the Invention
This invention relates generally to a lens control unit and a lens device for a TV camera, and more particularly to a lens control unit that electrically controls the focus, zoom, etc. of a lens device used for a TV camera, and the lens device.
2. Description of Related Art
Japanese Patent Provisional Publication Nos. 7-274053 and 9-304680 disclose a conventional TV camera, in which a lens device connects to a control unit, which is operated by a cameraman to control the zoom and focus of the lens device, through a multiple-conductor cable, and the control unit controls the zoom and focus with analog voltage signals. The control unit has recently been provided with a variety of ON/OFF switches and many functions such as controlling an extender in addition to the function of controlling the zoom and focus. At present, the cable connecting the control unit and the lens device merely includes about ten to thirty conductors, and hence, it is difficult to add new functions to the control unit.
To solve the above-mentioned problem, it may be considered to perform serial communication for connecting the control unit and the lens device to thereby transmit a variety of signals in a digital mode through a cable with a small number of conductors. However, the lens device and the control unit are detachably connected through connectors, and the lens device and the control unit are not always used in the same combination. A control unit in the digital mode cannot be connected to a lens device that cannot be operated with digital signals. This causes a problem when the components are replaced in emergency.
In view of the foregoing, it is therefore an object of the invention to provide a lens control unit for a TV camera, which is able to output control signals in both analog and digital modes, switch the modes according to a control mode of the lens device, or output the control signals in both analog and digital modes at the same time, and a lens device controlled by the lens control unit.
To achieve the above-mentioned object, the present invention is directed to a lens control unit electrically connecting to a lens device of a TV camera to control at least one of zoom, focus, iris and macro of the lens device, the lens control unit comprising: a first control signal generator for generating an analog control signal; and a second control signal generator for generating a digital control signal; wherein the lens control unit outputs both the analog control signal and the digital control signal to control the lens device.
The lens control unit of the present invention operates in both the analog mode and the digital mode, and outputs the control signals in both modes to the lens device simultaneously or selectively. Then, the lens device receiving the control signals selects either one mode. Thus, one control unit can control both the lens device in the analog mode and the lens device in the digital mode.
Hence, the lens devices and the control units can be combined more freely than before, and the components can easily be replaced in emergency. To achieve the above-mentioned object, the present invention is directed to a lens control unit electrically connecting to a lens device of a TV camera to control at least one of zoom, focus, iris and macro of the lens device, the lens control unit comprising: a first control signal generator for generating an analog control signal; a second control signal generator for generating a digital control signal; a detector for detecting a mode switch signal outputted from the lens device; and a mode selector for selecting a mode of the lens control unit from an analog mode and a digital mode in accordance with the mode switch signal detected by the detector; wherein the lens control unit outputs one of the analog control signal and the digital control signal in the mode selected by the mode selector to control the lens device.
The lens control unit of the present invention operates in both the analog mode and the digital mode, and detects the mode switch signal transmitted from the lens device by the detector to select the mode of the control signal from the analog and digital modes in accordance with the lens device. Thus, one control unit can control both the lens device in the analog mode and the lens device in the digital mode.
If the lens control unit receives the mode switch signal from the lens device to select the mode of the control signal as stated above, it is necessary to provide a signal line for transmitting the mode switch signal. Usually, however, there is no extra line in a multiple-conductor cable connecting the control unit and the lens device, and it is therefore impossible to provide a special line for transmitting the mode switch signal.
The lens control unit further comprising: an answer signal line for transmitting an answer signal outputted from the lens device, the answer signal representing at least one of states of the zoom, the focus, the iris and the macro of the lens device; wherein the mode switch signal has a frequency different from the answer signal, and the detector detects the mode switch signal through the answer signal line without a special line for the mode switch signal. Thus, the signal with the unexpected frequency for the normal answer signal is used as the mode switch signal and is superimposed on the line of the answer signal. The mode switch signal can be detected separately from the normal answer signal.
In the above-mentioned case, a lens device controlled by the lens control unit comprises: a mode switch signal generator for generating the mode switch signal selecting the mode of the lens control unit; wherein the lens device outputs an answer signal representing at least one of states of the zoom, the focus, the iris and the macro of the lens device, and the mode switch signal has a frequency different from the answer signal.